Olefin oxides constitute a valuable group of organic chemicals which are useful for the preparation of other chemical and industrial products. Propylene oxide, for example, is used in the preparation of propylene and polypropylene glycols. The major uses of propylene glycol are in resins, cellophane, hydraulic fluids, tobacco humectant and cosmetics. Polypropylene glycols are used in the production of polyurethanes. Other uses of propylene oxide are in isopropanolamines, glycol ethers for hydraulic fluids, surfactants and demulsifiers.
A well known process for the production of olefin oxides is the conventional chlorohydrin process. In that process, olefin, chlorine and water are mixed in a reaction vessel. The water and the chlorine form hypochlorous acid that reacts rapidly with the olefin to form chlorohydrin. Following the chlorohydrin reacts with slaked lime to form the corresponding olefin oxide. Conventional chlorohydrin processes for the production of ethylene and propylene oxides are described in J. A. Kent, Riegel's Handbook of Industrial Chemistry 779-80, 795-96 (1974). The conventional chlorohydrin process generates large amounts of undesirable by-products such as olefin dichlorides and olefin glycols.
Other well known processes for the production of olefin oxides are electrolytic chlorohydrin processes. Several electrolytic chlorohydrin processes that have been used in the past are described in U.S. Pat. Nos. 3,288,692, 3,394,059, 3,427,235, 3,635,803; German Pat. No. 1,176,649; and, T. Bejerano et al. The Electrochemical Production of Propylene Oxide in a Small Pilot Plant, 58 Trans. I. Chem. E. 28-32 (1980).
U.S. Pat. No. 3,288,692 discloses a process which comprises electrolysing an aqueous medium having a metal halide electrolyte while introducing an olefin to the vicinity of the anode of the electrolyte reaction zone to produce olefin oxide. The cell utilized may be of the diaphragm or diaphragmless type. The electrolyte and the olefin flow to the cell via two different lines.
U.S. Pat. No. 3,394,059 discloses a process for electrolytically oxidizing olefin to olefin oxides in a diaphragmless cell in the presence of an aqueous electrolyte which contains an acqueous bromide salt. According to the process disclosure, carbonate salt could be added to the electrolyte to increase its electrical conductivity. Olefin is introduced as vapor into the electrolyte that is already present in the cell.
U.S. Pat. No. 3,427,235 discloses a process of electrolytically oxidizing an olefin to an olefin oxide in an aqueous electrolyte. Oxygen that is generated at the oxide surface of the cell reacts with the olefin to produce the olefin oxide.
U.S. Pat. No. 3,635,803 discloses a process for producing an olefin oxide by mixing an olefin with an electrolyte containing an acetate and by subjecting the mixture to electrolysis. Vapor olefin is introduced into the electrolyte in the cell via a glass frit to form olefin bubbles in the electrolyte.
United Kingdon Patent Specification No. 1,176,649 discloses an electrolytc process for producing olefin oxides from olefins by using among other things an aqueous electrolyte containing a metal halide. The process is carried out in a cell having a diaphragm made out of thermoplastic material.
One disadvantage of the previous processes is that the methods of mixing the olefin and the electrolyte are inadequate whereby the processes have been ineffecient due to poor mixing. Another disadvantage of those processes is that they form a large amount of undesirable by-products including olefin dihalides and olefin glycols.
The present invention discloses a new process that provides better mixing between the electrolyte and the olefin, increases the surface area between the electrolyte and the olefin and reduces the formation of undesirable by-products. These and other advantages of the present invention will become apparent from the following description.